TITLE: this is an example of a linear growth
model for a continuous outcome with time-
invariant and time-varying covariates
DATA: FILE IS ex6.10.dat;
VARIABLE: NAMES ARE y11-y14 x1 x2 a31-a34;
MODEL: i s | y11@0 y12@1 y13@2 y14@3;
i s ON x1 x2;
y11 ON a31;
y12 ON a32;
y13 ON a33;
y14 ON a34;